The present invention relates to a rotary pump that serves for example as an oil pump for motor vehicles.
Various types of oil pump such as an internal gear pump and a plunger pump have been proposed to supply lubricating oil to an internal combustion engine, and working oil to a power steering for motor vehicles.
As for internal combustion engines for motor vehicles, a Wankel-type rotary engine is known, in addition to a reciprocating engine, which continuously carries out four strokes of suction, compression, expansion, and exhaust per rotation of a rotor contacting a trochoid curved surface (see JP-U 64-15726).
An outline of the Wankel-type rotary engine will be described. Side housings are arranged to both side faces of a rotary housing having a peritrochoid curved surface on the inner periphery thereof. A substantially triangular rotor is accommodated in the rotary housing to be rotatable while contacting the peritrochoid curved surface. Three working chambers are defined by the outer periphery of the rotor and the peritrochoid curved surface of the rotary housing. An output shaft or a crankshaft arranged through the side housings has a predetermined outer peripheral portion with which a disk-like eccentric portion is integrally formed having the center eccentric to the axis of the output shaft. The inner periphery of the rotor is supported on the outer periphery of the eccentric portion. A small-diameter stationary gear is fixed on the inner periphery of an output-shaft through hole of one of the side housings to face the working chambers. A rotor gear is formed to the inner periphery of the rotor on one end side thereof to engage with the stationary gear.
The rotary housing has parallel suction and exhaust ports formed at one side thereof, and a pair of ignition plugs mounted at another side thereof.
Rotation of the rotor after engine start causes rotation of the eccentric portion and the output shaft, and that of the rotor gear and the stationary gear engaged with each other, so that a vertex of the rotor makes rotation in tracing a peritrochoid curve or a fundamental curve of the rotary housing, transmitting power to the output shaft. That is, rotation of the rotor opens the suction port to start the suction stroke, which gradually increase the volume of the two working chambers. When this volume reaches the maximum value, the suction port is automatically closed. Then, fuel-air mixture within the working chambers is compressed, and ignited in the vicinity of the top dead center of the compression stroke, proceeding to the expansion stroke. After the expansion stroke, the exhaust port is opened to complete the exhaust stroke, proceeding again to the suction stroke. This process produces three rotations of the output shaft per rotation of the rotor, transmitting power to the output shaft.
Recently, due to its extremely high power efficiency, an attempt is made to apply the fundamental structure of such four-stroke one-cycle rotary engine to the oil pump for motor vehicles, etc. However, since the rotary engine, which is concerned in compressible fluid such as fuel-air mixture, serves as an engine in accordance with the compression and expansion strokes of compressible fluid, i.e., a volume change of the working chambers, the rotary engine cannot serve as an oil pump that for non-compressible fluid such as oil. That is, the non-compressible nature of fluid in accordance with a great volume change of the working chambers, makes it impossible for the rotary engine to serve as an oil pump.
It is, therefore, an object of the present invention to provide a rotary pump which is constructed with the fundamental structure of the rotary engine.